[Mp4-tech] Reg diff bt 3gp&mp4

[Dave Singer]

At 3:43 PM +0100 7/21/04, Pradeep kumar wrote:
>hi, what is the differences between 3gp and mp4 format? Can a 3gp 
>decoder will run mp4 files, what are the modifications to be done ?

3GP and MP4 files are based on the same structure.  However, there 
are differences in codecs and some ancillary details.  Here are the 
most obvious.
a) MP4 files normally contain at least basic support for the MPEG-4 
systems structures, including an initial object descriptor, and at 
least a minimal BIFS and object descriptor stream (see the ISMA specs 
for an example).  These are not required in 3GPP.
b) 3GPP uses H.263 video, and AMR and AMR-WB audio;  these codecs are 
not part of MPEG-4.  The specs share MPEG-4 video and AAC audio, but 
3GPP selects only some profiles and bit-rates.
c) MPEG-4 has many other codecs and sub-systems that are not used by 
3GPP (e.g. TwinVQ, HVXC, HILN, CELP audio, and so on).
Many 3GPP players can play MP4 files as well, as long as the codecs 
are in the compatible set, and the bit-rates and profiles are 
suitable.
-- 
David Singer
Apple Computer/QuickTime